1. Field
Exemplary embodiments of the following description relate to an optical apparatus, a light screening apparatus, and an electronic device including the light screening apparatus.
2. Description of the Related Art
A light screening apparatus is a device that transmits or blocks incident light. An optical shutter, which is one type of light screening apparatus, is used to selectively transmit or block light. For example, an optical shutter included in a camera selectively transmits light passing through the camera's lens and to an image sensor. Generally, such a camera controls a time period during which light is transmitted to the image sensor and/or the amount of light incident on the image sensor by controlling an operating speed of the optical shutter and/or an opening size of an aperture of the camera. Light screening apparatuses such as optical shutters have been utilized for various electronic devices, such as optical switching devices, which require a permanent or temporary light-screening function, or require a selective blocking or transmitting of incident light.
There are different types of optical shutters including mechanically operating optical shutters and electronically operating optical shutters. In an electronically operating optical shutter, an on/off status of an image sensor is controlled in order to control a time during which the image sensor receives light or to limit the amount of light received by the image sensor. Since an electronically operating optical shutter operates according to a predetermined circuit configuration, electronically operating optical shutters have been widely used in a portable digital cameras. However, such electronically operating optical shutters have a drawback in that image dragging may occur as the number of pixels included in a camera module increases. Image dragging generally occurs in electronic rolling shutter (ERS) systems because an image in an ERS system is captured by activating the image sensors sequentially from one corner (e.g. the left, top corner) to an opposite corner (e.g. the right, bottom corner) of the pixel matrix. Therefore, when an object is moving quickly, there is a position change of the object during the time that the image sensors are being sequentially activated. This causes an unwanted image dragging effect.
Recently, the number of pixels in a camera module for a mobile device, such as a mobile phone, a gaming device, a camera or the like, has been increased significantly in order to obtain a high quality image, and thus the interest in a mechanically operating optical shutters has increased. A recent tendency in the mobile device industry is to make the device smaller and thinner, and thus mechanically operating optical shutters need to be smaller and thinner while continuing to operate with a fast response (shuttering) speed. Korean patent application publication No. 2009-0055996, published on Jun. 30, 2009, entitled “Shutter and Micro Camera Module Having the Same” describes an example of a mechanically operating optical shutter that uses a plurality of rollup blades to achieve a high response speed.
Most electronic devices include a display device, such as a Liquid Crystal Display (LCD) touch screen. Demand for a display device providing high quality images and performance is continuously increasing. In order to meet these needs, manufacturing technologies for display devices have been improved significantly and continuously to obtain better display devices. Two different kinds of display devices have been developed for electronic devices. These are transmission-type devices and reflection-type devices. In a transmission-type display device, images are displayed using light transmitted through a panel, and in a reflection-type display device images are displayed using light reflected from a panel. Transmission-type display devices have high visibility in dark environments, but have relatively low visibility in bright outdoor or indoor environments. On the other hand, reflection-type display devices have visibility in dark environments, but have relatively high visibility in bright environments.
One type of translucent display device takes advantage of both transmission-type and reflection-type displays. This translucent display device can be selectively operated either in a reflection mode or in a transmission mode according to the brightness of a surrounding environment. Therefore, the translucent display device is very beneficial for use in a mobile electronic device which is operated in various lighting conditions. Generally, cells in the translucent display device are divided into two parts. One part of each of the cells has a reflection type structure, and the other part of each of the cells has a transmission type structure. As a result, the translucent display has a relatively low brightness compared to existing single-mode displays (i.e. a transmission-type display or a reflection-type display).